1. Field of the Invention
The present invention relates to a lip type seal corresponding to one kind of a sealing apparatus. The lip type seal in accordance with the present invention is used, for example, as a shaft seal which is applied to a water pump (W/P) for a vehicle such as a motor vehicle or the like, or used as a shaft seal which is applied to a W/P for a household appliance or a light-load industry or the like.
2. Description of the Conventional Art
Conventionally, as shown in FIG. 10, there has been known a lip type seal 81 which inhibits a sealed fluid within a machine from leaking to an ambient air side by being installed to an inner periphery of a shaft hole 72a of a housing 72 so as to slidably come into close contact with a peripheral surface of a shaft 74 which is inserted to the shaft hole 72a. This lip type seal 81 has a first seal lip 82 which is arranged in a sealed fluid side A and is made of a rubber-like elastic material, and a second seal lip 83 which is arranged in an ambient air side B and is made of a resin (refer to Japanese Unexamined Patent Publication No. 10-318377).
Since the conventional lip type seal 81 has a plurality of seal lips 82 and 83 each of which achieves a sealing action, it can achieve an excellent sealing effect, however, it causes a disadvantage in the following point.
At the request on recycle against an environmental problem in recent years, each of component parts of the lip type seal is requested to be disposed after being sorted on a material, however, in the conventional lip type seal 81, the first seal lip 82 made of the rubber-like elastic material is bonded through vulcanization to a reinforcing ring 84 made of a metal, and both the elements 82 and 84 are formed as an integral vulcanization molded product. Accordingly, it is impossible to easily separate and sort both the elements 82 and 84 at a time of disposing. Therefore, it is impossible to comply with the request on the recycle.
Consequently, the applicant of the present invention has previously proposed a lip type seal 91 which has a first lip seal member 92 which is provided with a first seal lip 93 arranged in a sealed fluid side A and is made of a rubber-like elastic material, a second lip seal member 94 which is provided with a second seal lip 95 arranged in an ambient air side B and is made of a resin, and two cases 96 and 97 which pinch both the lip seal members 92 and 94 from both sides in an axial direction and are made of a metal, and is structured such that these four parts are assembled in a non-bonding manner, as shown in FIG. 11 (refer to WO2004/076894A1). In accordance with this prior art, since each of the parts is not bonded, it is possible to easily separate and sort each of the parts, whereby it is possible to comply with the request on the recycle. However, in this prior art, there is room for improvement in the following point.
(1) Assembly Retaining Property Between Component Parts
In the lip type seal 91, two cases 96 and 97 respectively have annular flat surface sections 96a and 97a for pinching both the lip seal members 92 and 94 from both sides in the axial direction and are structured such that tubular sections 96b and 97b are integrally formed in the flat surface sections 96a and 97a. The tubular sections 96b and 97b are respectively fitted to an inner peripheral side of a cylinder section 92a of the first lip seal member 92 in the case 96 in the sealed fluid side A and press-fitted fixedly to an insertion hole 92b which is provided in the cylinder section 92a of the first lip seal member 92 in the case 97 in the ambient air side B. Therefore, each of the parts is retained in an assembled state by setting a fitting margin and a press-fit margin incident to the fitting and the press-fit, however, in the case that each of the parts is exposed to a force in the axial direction, any engaging structure for preventing the parts from being separated from each other in the axial direction is not particularly provided between the parts. Accordingly, if the case 96 in the sealed fluid side A is pulled in an axial direction (a direction of an arrow C) for detaching the lip type seal 91 in a state of being installed to an inner periphery of the shaft hole 72a of the housing 72, there is a case that only the case 96 is pulled out and the other parts are left in a state of being installed (alternatively, only the case 96 and the first lip seal member 92 may be pulled out, and the second lip seal member 94 and the case 97 in the ambient air side B may be left). This is caused by nothing but the fact that the assembly retaining force between the parts depends only on a friction force.
(2) Installation Workability
Further, in the lip type seal 91 mentioned above, two cases 96 and 97 do not particularly have any structure for defining a distance in the axial direction between them. Further, the first lip seal member 92 which is pinched between both the elements and is made of the rubber-like elastic material cannot achieve a sufficient sealing action unless it is used in a state of being compressed in the axial direction. In other words, there is fear that a leakage of the sealed fluid is caused from gaps with respect to the second lip seal member 94 made of the resin and the case 97 in the ambient air side B. Accordingly, at a time of installing the lip type seal 91 mentioned above, the lip type seal 91 is contacted to a step section 98 which is provided in an inner periphery of the shaft hole 72a of the housing 72, and is installed by using a snap ring 99 while applying a compression load in the axial direction, whereby the lip type seal 91 is installed in a state in which a whole thereof is compressed in the axial direction between the step section 98 and the snap ring 99. However, there is such a disadvantage that a work of installing by using the snap ring 99 while applying the compression load in the axial direction as mentioned above is extremely complicated.
Further, since the annular insertion hole 92b which is open to the ambient air side B is provided in the cylinder section 92a of the first lip seal member 92, a position in an outer peripheral side than the insertion hole 92b in the cylinder section 92a is formed into such a shape that the ambient air side end portion 92c is terminated while remaining in the cylindrical shape. Therefore, since the ambient air side end portion 92c rubs against an inner peripheral surface of the shaft hole 72a at a time of inserting the first lip seal member 92 to an inner periphery of the shaft hole 72a of the housing 72, there is a case that evagination is caused in the ambient side end portion 92c. 
Further, in a bonding type lip seal in which the seal lip 82 made of the rubber-like elastic material is bonded through vulcanization to the reinforcing ring 84 made of the metal as shown in FIG. 10, a problem in resistance against foaming is pointed out. In conjunction with a high speed and a high temperature of an engine in recent years, cooling water of a water pump for cooling the engine tends to have a high temperature and a high pressure, and an ambient atmosphere of the seal section becomes harsh. Under the use condition mentioned above, in the bonding type lip seal mentioned above, since the seal lip 82 made of the rubber-like elastic material and the reinforcing ring 84 made of the metal are bonded, there is a case that a foaming phenomenon is caused in the seal lip 82 in the case of being used under a high load condition, and this causes a reduction of a sealing performance.